No small dilemma: small bowel volvulus mimicking acute coronary syndrome

Abstract Acute abdominal pathologies can cause electrocardiogram (ECG) changes mimicking an acute coronary syndrome (ACS), resulting in diagnostic uncertainty and delay. We report a 65-year-old male with multiple risk factors for ACS who presented with four hours of progressive epigastric and chest pain that resolved in the emergency department. ECG findings were concerning for new deeply inverted T-waves with normal troponins, raising concerns for Wellens Syndrome. Emergent heart catheterization was negative but abdominal computed tomography angiography showed occlusion of the superior mesenteric vessels. Subsequent exploratory laparotomy revealed a small bowel volvulus with extensive necrosis, resulting in a 430 cm resection.


Introduction
ST-elevation myocardial infarctions (STEMIs) are medical emergencies and a door-to-balloon time of 90 min or less is recommended as best practice [1,2].Deeply inverted or biphasic Twaves in the precordial leads with minimal or no ST elevations raise concerns for Wellens Syndrome, which is a well-documented STEMI-equivalent finding that typically involves stenosis of the proximal portion of the left anterior descending (LAD) coronary artery [3].However, dynamic ECG changes, like those seen in Wellens Syndrome, can also occur in acute abdominal pathologies such as mesenteric ischemia, appendicitis, bowel obstruction, pancreatitis, and cholecystitis (Table 1).Here, we present the first reported case of small bowel volvulus with necrosis presenting with an ischemic pattern on ECG concerning for Wellens Syndrome and no significant ischemia on coronary angiography, along with a review of the available case reports for abdominal pathology induced ischemic changes on ECG.

Case report
A 65-year-old male active smoker with a history of non-ischemic cardiomyopathy, hypertension, and hyperlipidemia was brought to the hospital by ambulance after four hours of progressive epigastric and chest pain.During transit, ECG showed ST elevation in the anterior-lateral leads (Fig. 1).Repeat ECG In the emergency department revealed an accelerated junctional rhythm with minimal ST elevation in V3, lack of Q-waves, and new deeply inverted T waves in V2-V4 (Fig. 2).Physical examination showed stable hemodynamics, a distressed appearance with diaphoresis, and epigastric tenderness with guarding.Initial lab results showed an undetectable troponin level but elevated serum lactate of 5.8 mmol/l.The patient was emergently taken for left heart catheterization for concern of acute coronary syndrome (ACS).However, the catheterization showed no significant coronary disease and normal filling pressures.Post-procedurally, the patient continued to experience severe abdominal pain.A computed tomography angiography (CTA) of the abdomen suggested occlusion of the superior mesenteric artery and vein with extensive small bowel ischemia (Fig. 3).During the exploratory laparotomy, the vascular team discovered a small bowel volvulus with necrotic bowel extending from the mid-jejunum to the terminal ileum, requiring an extensive 430 cm small bowel resection by general surgery.Post-laparotomy ECG showed resolution of all previously noted changes and normalization of lactic acid levels (1.9 mmol/l).

Discussion
Wellens Syndrome on ECG consists of deeply inverted or biphasic T-waves in multiple precordial leads, coupled with an isoelectric or minimally elevated ST-segment (<1 mm), lack of Q-waves, and preservation of normal R-wave progression [3,4].This ECG pattern was first identified by de Zwaan et al in 18% of patients admitted for unstable angina [3].Among these patients, 75% who did not undergo coronary revascularization eventually experienced ECG changes and chest discomfort resolved 30 min after admission.a severe anterior wall infarction within a few weeks [3].Subsequently, a study by the same researchers confirmed a 100% association with significant proximal LAD artery blockage, ranging from 50% to complete obstruction [5].As a result of these findings, Wellens syndrome is considered a "STEMI-equivalent," despite cardiac enzyme levels being usually normal or only slightly elevated [3,4].Unfortunately, our patient lacked the normal R-wave progression due to left ventricular hypertrophy, thereby cannot be considered to have true Wellens Syndrome.Nonetheless, new T-wave inversions >2 mm in anterior leads as a sole indicator have a high positive predictive value (86%), sensitivity (69%), and specificity (89%) for significant LAD disease [6].Definitive management in either case involves urgent coronary angiography to assess the severity of coronary artery blockage [4].However, ECG changes are not solely related to cardiac pathology.In the existing literature, several case reports describe transient ischemic ECG patterns associated with acute abdominal pathologies resembling ACS.This includes three cases of mesenteric ischemia presenting as ST elevation on ECG.The first case involved a novel presentation of mesenteric ischemia mimicking inferior STEMI in a 61-year-old male who presented with epigastric pain, vomiting, diarrhea, and an increase in troponin levels.ECG changes resolved following right hemicolectomy [7].Another case represents a rare presentation of small bowel strangulation due to adhesions, which caused bowel infarction in a 63year-old female who exhibited borderline anterior ST elevation and developed Takotsubo cardiomyopathy secondary to physical stress [8].The last case involved stress-induced cardiomyopathy in a 70-year-old female who presented with acute-onset chest pain, inferior ST elevation, rising troponin levels, and elevated lactate, leading to caecum resection and subsequent ECG normalization [9].T-wave inversions and ST changes can also be observed in acute pancreatitis, acute cholecystitis, gastric distention, and bowel obstruction.Table 1 summarizes some remarkable cases resembling ACS.
The underlying pathophysiology of dynamic ECG changes seen with acute abdominal pathologies remains unclear and has not been fully investigated or published.It is likely a multifactorial process and several mechanisms have been proposed.The first mechanism involves the distension of a hollow organ, which can directly compress or displace the heart within the thoracic cavity [10].Similarly, increased intra-abdominal pressure can result in the relative displacement or compression of the inferior surface of the heart, leading to changes in the QRS axis and/or voltage.A second proposed mechanism is based on the occurrence of a vasovagal ref lex due to gastrointestinal tract distention.This visceral-cardiac ref lex causes increased vagal tone, potentially causing ECG changes and transient coronary vasospasm.Finally, a similar mechanism to Takotsubo cardiomyopathy has been proposed, where an exaggerated sympathetic stimulation and elevated plasma catecholamines due to emotional or physical stress results in microvascular spasm or dysfunction with myocardial stunning [11,12].
Our case was particularly challenging because the patient presented with symptoms consistent with ACS, in addition to an abnormal abdominal exam and gastrointestinal complaints.Given the presence of significant coronary risk factors, STEMIequivalent ECG changes, and timing recommended by the societal guidelines, cardiac evaluation took precedence.Unfortunately, this prioritization resulted in a delay in diagnosing small bowel volvulus with mesenteric ischemia, which triggered one or more of the pathophysiological mechanisms described above, resulting in Wellens T's on ECG concerning for ischemia.
In summary, associating ischemic patterns on ECG with ACS is crucial, but it may be equally important to consider abdominal ischemia.A delay in diagnosing bowel ischemia contributes to the extent of tissue ischemia and resultant necrosis, as it similarly does to the heart and other organs.To the best of our knowledge, this is the first reported case of small bowel volvulus induced mesenteric ischemia presenting with ischemic patterns on ECG.We believe it highlights the unique association between ischemic changes on ECG and abdominal pathology, which can present the physician with a life-threatening diagnostic dilemma when timely cardiac or abdominal reperfusion is crucial.

Figure 1 .
Figure 1.ECG taken en route to the Emergency Department showing ST elevation in the anterior-lateral leads.

Figure 2 .
Figure 2. ECG in the Emergency Department revealing an accelerated junctional rhythm with minimal ST elevation in V3, and new deeply inverted T waves in V2-V4 consistent with Wellen's T's, concerning for ischemic changes.

Figure 3 .
Figure 3. Computed tomography angiography of the abdomen with areas of "swirls" (white arrows) concerning for volvulus.A, axial and B, coronal views.

Table 1 .
Summary of acute abdominal pathology cases presenting with transient ischemic ECG patterns, resembling acute coronary syndromes